text: * Lower aeration requirements decrease energy consumption and aeration costs for 20 percent if compared with conventional single stage activated sludge plant.
  * The volumes of aeration tanks are 40% lower if compared with conventional single stage activated sludge plant.
  * Increased sludge production in the A-stage results in increased biogas production in the digester (for plants with anaerobic digestion of excess sludge).
  * Stability towards the shock loads (pH, chemical oxygen demand (COD), toxic substances) explained by the wide-ranging biochemical potential, high mutation capacity and adaptability of sludge in the A-stage.
  * A-stage can receive higher organic loads than conventional activated sludge systems.
  * Effluent concentrations are more stable because of the two-stage process configuration employed.
  * Heavy metals are mainly removed with the A-stage sludge. Therefore, B-stage sludge has lower concentrations of heavy metals than sludge from conventional activated sludge process and may comply with the agricultural standards.